Air-Cleaning, Heat-Exchange Apparatus

The present invention relates in general to air-cleaning apparata and in particular to such apparata which also achieve heat exchange and heat transfer.

Industrial exhaust poses a major problem from the standpoint of pollution, and with the promulgation of federal rules and regulations and clean air standards, many efforts have been focused on how to reduce the level of contaminants from the effluent wastes. A related problem occurs in the area of restaurant exhaust from areas such as grills and broilers. Restaurants, especially fast-food restaurants, generate large amounts of grease-laden exhaust from the frying and broiling of the various food items which are prepared. This grease-laden exhaust is typically drawn up through a kitchen hood and exhaust duct combination to the atmosphere by a large ventilating fan arrangement. The problem with this type of design is that the grease from the exhaust collects on the internal surfaces of the hood, the exhaust duct and the fan arrangement and must be periodically cleaned. The frequency of required cleaning depends upon the volume of exhaust and the amount of grease, but a cleaning frequency of once a month is very often advisable in order to assure that grease levels will not reach the point where a fire occurring in the kitchen area will spread to and ignite this grease. Unfortunately, the thorough cleaning of the grease from the hood, exhaust duct and ventilating fan arrangement is difficult and is often quite time consuming and represents significant downtime to the particular restaurant. As a result of the inconvenience represented by the cleaning procedure, removal of the grease from the internal surfaces is not always performed when required. A somewhat predictable consequence of this lack of proper and periodic cleaning is that the hood, exhaust duct and fan arrangement will become heavily grease coated as well as producing a noticeable odor. Significant fire disasters have occurred where a grease fire in the kitchen exhaust duct was attributed to be a cause or at least a contributing factor to the spreading of the fire.

Recently efforts have been made to chemically treat such grease-laden exhaust so that the grease is emulsified and its buildup on internal surfaces is reduced. By using a mist-like spray of a chemical and water mixture directed around the inside of the exhaust duct between the hood and ventilating fan, the emulsified grease is either drained off in liquid form or may be exhausted in vapor form. Although this method has proved effective to prevent a majority of the grease buildup in the exhaust duct and on the ventilating fan, there remain certain shortcomings and disadvantages.

The spray arrangement just mentioned must have its volume of chemical solution governed by the volume of exhaust and the amount of grease, and to be effective, the sprayer must direct a mist against the full inside perimeter of the exhaust duct so that all surfaces can be cleaned of grease. This poses a very exacting requirement on the design of the spray nozzle head as well as its positioning within the exhaust duct. However, even with well designed and positioned spray nozzle heads, the grease which is emulsified by the chemical solution spray does not represent 100 percent of the grease flowing through the exhaust duct and the emulsified grease which is exhausted in vapor form, as well as the grease which is not chemically treated, still contributes to the pollution of the atmosphere. Another very significant factor, especially with energy consideration concerns, is the amount of heat which is generated by the restaurant grills and broilers and is lost up the exhaust duct. Any attempt to capture this heat and reuse it for general heating of the structure runs headlong into the related problems of grease accumulation. If a heat exchanger is employed, once the convecting surfaces, such as the fins, collect a thin film of grease, the heat-transfer properties of such convecting surfaces are reduced to the point that the heat exchanger becomes highly inefficient. This grease buildup acts as a thermal insulator and prevents efficient heat transfer from the hot exhaust gas to a heat-absorptive fluid circulating through the heat exchanger. Related problems involve how to extract a majority of this exhaust duct heat so that system efficiency is high and how can the complete system be maintained in a virtually grease-free manner while still not exhausting harmful pollutants (such as emulsified grease) into the atmosphere. A collateral benefit of grease removal is that the accompanying odor will also be eliminated. The shortcomings and disadvantages discussed above are overcome by the apparatus of the present invention which is disclosed herein.

A heat-exchange apparatus incorporating contaminant removal means for extracting heat from a hot, gaseous flow stream while simultaneously removing contaminant material from the hot, gaseous flow stream according to one embodiment of the present invention comprises a three-stage, heat-exchange arrangement centrally disposed within the hot, gaseous flow stream and includes first, second and third heat exchangers, a source of chemical solution, the contaminant material being soluble in the chemical solution, chemical solution spray means directed toward the first heat exchanger for reducing buildup of the contaminant material on the external surfaces of the first heat exchanger and a mist eliminator positioned in the hot gaseous flow stream between the first and second heat exchangers.

One object of the present invention is to provide an improved exhaust-cleaning, heat-exchange apparatus.

Related objects and advantages of the present invention will be apparent from the following description.

FIG. 1 is a fragmentary, perspective view of an exhaust-cleaning, heat-exchange apparatus according to a typical embodiment of the present invention.

FIG. 2 is a sectioned, end elevation view of the FIG. 1 apparatus as taken along line 2--2 in FIG. 1.

FIG. 3 is a sectioned, end elevation view of the FIG. 1 apparatus as taken along line 3--3 in FIG. 1.

FIG. 4 is a sectioned, end elevation view of the FIG. 1 apparatus as taken along line 4--4 in FIG. 1.

FIG. 5 is a fragmentary, partial plan view of one end of the FIG. 1 apparatus.

FIG. 6 is a fragmentary, partial side elevation view of another end of the FIG. 1 apparatus as taken along line 6--6 in FIG. 4.

FIG. 7 is a schematic flow diagram of a fluid flow pattern associated with the FIG. 1 apparatus.

FIG. 8 is a block diagram of an exhaust gas flow path associated with the FIG. 1 apparatus.

For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated device, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.

Referring to FIG. 1, there is illustrated exhaust-cleaning, heat-exchange apparatus 20 which includes a main housing portion 21, a first fan arrangement 22, a second fan arrangement 23 and a plurality of dial indicators 24, 25, 26, 27 and 28 whose functions will be described hereinafter. Main housing portion 21 includes a top skin 29 which is insulated by a thickness of insulation 30 disposed on the inner surface, a lower skin 31 fabricated of expanded metal which is sealingly joined to the lower perimeter edge of top skin 29 and a connecting duct portion 32 which encloses the free end 33 of apparatus 20 between top skin 29 and lower skin 31. An intermediate duct section (not shown in FIG. 1) connects second fan arrangement 23 with connecting duct portion 32 for structural rigidity and an efficient flow pattern.

First fan arrangement 22 is sealingly joined at one flanged end of arrangement 22 around a circular opening in top skin 29 at first end 36 of apparatus 20. The opposite flanged end of first fan arrangement 22 is sealingly joined around the perimeter of exhaust stack 37. Although exhaust stack 37 may represent virtually any suitable duct of a structure through which contaminant material is exhausted, typically in gaseous form, in the preferred embodiment exhaust stack 37 is the exhaust duct extending from a restaurant kitchen area and the hot exhaust gas which flows up through exhaust stack 37 is typically heavily grease laden. Apparatus 20 includes a central flow passageway which extends from first end 36 to opposite free end 33 and is enclosed by top skin 29 in combination with lower skin 31. Inasmuch as the circular opening in first end 36 represents the sole point of entry into apparatus 20 for the hot exhaust gas from exhaust stack 37, apparatus 20 which draws this hot exhaust gas into its interior by means of the two fan arrangements, functions as a closed system. As this hot exhaust gas flows through apparatus 20, heat is extracted by a series of heat exchangers while any grease which is deposited on the internal surfaces of apparatus 20 is removed by a chemical solution spray directed at these internal surfaces. Consequently, the flow of exhaust gas which is present at end 33 is lower in temperature than the entering exhaust gas at end 36 and the grease which was contained within the entering exhaust gas is removed by the time the exhaust gas reaches free end 33. The exhaust gas present at end 33 is pulled into the lower portion of apparatus 20 by means of the second fan arrangement 23. As this still-warm exhaust gas passes into this lower region, which is surrounded by lower skin 31, a certain degree of heat will be transferred to the internal and surrounding portions of apparatus 20 thereby providing a blanket of warm air and reducing the effect of a severely cold temperature exterior to apparatus 20. This feature is important inasmuch as apparatus 20 is typically located on the roof of a structure and is exposed to all types of environmental conditions, including extremely cold temperatures. Due to the fact that one feature of apparatus 20 is the extraction of heat from the entering hot exhaust gas, it is important that heat losses to the atmosphere be reduced to as great a degree as possible. This warm, clean exhaust gas from free end 33 assists in this heat loss reduction by acting as a buffer between the heat exchangers and the atmosphere.

In the operation of a restaurant kitchen, what typically occurs is that grease-laden exhaust from broilers and grills is drawn up through a suitable exhaust hood and duct arrangement by means of a suitable ventilating fan. As the particles of grease which are within this exhaust come in contact with the various internal surfaces of the exhaust duct and the ventilating fan, grease is deposited on these surfaces. After only a brief period of operation, the grease level becomes critical with respect to efficiency of the ventilating fan as well as representing a potential fire hazard. The present invention provides an apparatus which is connectable to such an exhaust duct and provides means by which grease buildup on internal surfaces may be virtually eliminated while at the same time extracting heat from this hot exhaust gas which can be utilized to supplement some of the heating requirements for the structure with which apparatus 20 is associated. When apparatus 20 is employed, as will be described hereinafter, a ventilating fan located within the exhaust stack is not required inasmuch as first fan arrangement 22 provides the necessary pulling draft for removal of the exhaust from the kitchen area. First fan arrangement 22 sealingly joins to exhaust stack 37 in a suitable manner which does not permit exhaust leakage. Surrounding first fan arrangement 22 is a small cover portion 38 which connects to and completely around the flange of the first fan arrangement 22 and also to top skin 29 so as to enclose first fan arrangement 22. The opposite flanged end of fan arrangement 22 sealingly joins to the circular opening in top skin 29 as has been previously discussed. Located within top skin 29 is a cylindrical drum member 39 (see FIGS. 2 and 4) which extends for approximately one-half the overall length of apparatus 20 beginning at first end 36. The first end 40 of drum member 39 is located adjacent first fan arrangement 22 and drum member 39 is structurally arranged so as to be rotatable with respect to first fan arrangement as will be described in greater detail hereinafter. By sealingly arranging flanged end 41 in alignment with first end 40 of drum member 39, virtually all the hot exhaust gas which is drawn up through exhaust stack 37 will be pushed by first fan arrangement 22 into and through drum member 39. However, due to the fact that the drum member rotates with respect to the fan arrangement a slight clearance is provided. Since this clearance permits some leakage of the entering hot exhaust gas to occur, cover 38 creates an enclosure which limits such leakage and prevents leakage to the atmosphere.

Apparatus 20 further includes a structural frame fabricated from aluminum angles and square aluminum tubing which is arranged so as to provide four leg-like support members and a box-like structure thereabove. Although drum member 39 is positioned within the confines of this box-like frame structure, member 39 is thermally insulated therefrom and mechanically separated therefrom such that the entire support for drum member 39 with respect to the structural frame is by means of an arrangement of drive rollers and idle rollers. Drum member 39 rests upon a pair of idle rollers 44 and 45 which are disposed beneath drum member 39, rotatably fixed to the box-like frame structure, and adjacent end 40. Although only idle roller 44 is illustrated in FIG. 4, it is to be understood that idle roller 45 is in line with idle roller 44 but on the opposite side of drum member 39. Drive rollers 46 and 47 are disposed at the opposite second end 48 of drum member 39 and are rotatably fixed to their correspondingly adjacent portion of the box-like frame structure. Rollers 46 and 47 act in combination with a belt drive and gear motor to provide rotation to drum member 39. Also adjacent second end 48 of drum member 39 are two additional idle rollers 49 and 50 which provide a retaining and steadying feature to the rotation of drum member 39 to rigidly hold drum member 39 in contact with drive rollers 46 and 47 as well as drive belt 53 a portion of which extends between drive rollers 46 and 47 and contacts the underside portion of drum member 39. Drum member 39 includes a cylindrical metal body portion 54, an outer layer of insulation 55, an inner end lip portion 56 which extends completely around first end 40 of drum member 39 for retaining fluid which may collect within cylindrical body member 54 and an exterior air seal 57 which rotates with drum member 39 and provides additional sealing properties to prevent excess hot exhaust gas leakage. A guide roller 51 is provided at first end 40 for assisting in controlling any longitudinal shift of drum member 39.

Disposed within cylindrical body member 54 of drum member 39 is a first heat exchanger 58 which includes a first tapered, spiralled arrangement 59 of copper tubing having its larger diameter end adjacent end 40 and which extends from a location adjacent end 40 to a second location adjacent end 48. Heat exchanger 58 further includes a second tapered, spiralled arrangement 60 also of copper tubing which criss-crosses with the first spiralled arrangement 59 in that the smaller diameter end of arrangement 60 is adjacent end 40. The flow passageway through first arrangement 59 and the flow passageway through second arrangement 60 are tied together at common points such that as a heat-absorptive fluid is circulated through this copper tubing, heat transfer to the heat-absorptive fluid can be effected simultaneously from both arrangements. Consequently, as hot exhaust gas is pushed through apparatus 20 by means first fan arrangement 22, a portion of the heat within this hot exhaust gas will be transferred to the copper tubing which in turn will conduct its absorbed heat to the circulating heat-absorptive fluid passage therethrough. From this point, the hot exhaust gas, which is now at a somewhat lower temperature, passes further downstream through apparatus 20 where it flows across a mist eliminator 61 and passes therethrough and then across a second heat exchanger 62 and after that through and across a third heat exchanger 63. The structure and functions of the mist eliminator 61 and the second and third heat exchangers 62 and 63 will be described in greater detail hereinafter. At this point, it should be understood that mist eliminator 61 and heat exchangers 62 and 63 are located substantially central to the flow stream of the hot exhaust gas.

Although the heat-exchange aspects of apparatus 20 may be viewed as of a conventional nature and known to the art, it is to be pointed out that the particular arrangement of drum member 39 which is thermally insulated as a unit as well as from the surrounding portions of apparatus 20 provides a highly efficient heat transfer mechanism wherein heat losses to surrounding structural members or to the atmosphere are significantly reduced. The only contact which drum member 39 makes with the surrounding box-like frame structure is indirectly through the various idle rollers and drive rollers. Since these rollers are coated with a rubber or synthetic compound, any heat transfer is negligible. A further feature which contributes to the overall efficiency to the heat transfer between the hot exhaust gas and the heat-absorptive fluid in first arrangement 59 and second arrangement 60 is that the copper tubing of these arrangements is supported within drum member 39 by a minimal area of metal-to-metal contact. This is achieved by the use of bracket bars 66 and 67 which are rigidly joined to their corresponding arrangements of copper tubing and are force-retained within cylindrical body member 54 by means of bolts 68 which are threadedly received by the free ends of the various bracket bars at the larger diameter end of their respective arrangements and are threadedly advanced into pressure contact with the internal surfaces of cylindrical body member 54. There are four bracket bars 66 90 degrees apart associated with first arrangement 59 and there are similarly four bracket bars 67 associated with second arrangement 60. There are various options available to securely position the two arrangements within body member 54, such as, for example, clamping together the crossing points of corresponding pairs of bracket bars 66 and 67.

As a result of this minimal metal-to-metal contact arrangement, any heat loss or heat transfer from the copper tubing to the metal surface of cylindrical body member 54 must be through the bolts 68 and this minimal surface area of contact means that a minimal amount of heat transfer will occur. As previously mentioned, the hot exhaust gas which arrives through exhaust stack 37 is typically heavily grease laden. As this grease-laden exhaust gas flows up through exhaust stack 37, through first fan arrangement 22 and then into drum member 39, portions of this grease will be deposited on all internal surfaces of apparatus 20 which the grease-laden exhaust gas comes in contact with. In order to continuously maintain apparatus 20 as a wet system, a feature which greatly contributes to fire prevention, and to prevent any grease buildup from occurring on such internal surfaces, a chemical solution sprayer arrangement is provided which communicates with a suitable source of chemical solution for delivery into apparatus 20. Tubing line 69 couples to a source 70 of chemical solution and extends upwardly along support leg 71 to which it may be attached by means of suitable clips or brackets. At the approximate base of first fan arrangement 22, tubing line 69 splits into two different branches by means of a suitable tee fitting 73. Branch line 74 extends from tee fitting 73 over and into exhaust stack 37. The insertion of branch line 74 into exhaust stack 37 is by means of a sealed connection and the free end of branch line 74 is provided with a 160.degree. spray nozzle head which is centrally positioned within exhaust stack 37 and is directed outwardly toward the internal surfaces of exhaust stack 37 and upwardly toward first fan arrangement 22. As chemical solution is delivered through branch line 74 to nozzle head 75, a spray mist will be sprayed upon the internal surfaces of exhaust stack 37. Inasmuch as a chemical solution is selected in which the particular exhaust gas contaminant, such as, in this case grease, is soluble; contact of the spray mist with grease which has collected on these internal surfaces will cause the grease to go into liquid solution in emulsified form. Although such liquid solution may initially drain down exhaust stack 37 back toward the kitchen area of the restaurant, the continuing upward flow of hot exhaust gas will convert this emulsified grease-containing liquid into vapor form and will conduct it on through apparatus 20. Due to the fact that the grease has been broken down and placed in a solution wherein it is soluble, this grease will remain in liquid solution and not be deposited on subsequently contacted internal surfaces. However, the spray mist from nozzle head 75 is not typically effective to place all of the grease flowing through exhaust stack 37 into an emulsified condition due to the volume of exhaust and amount of grease. Consequently, some grease will be deposited on the internal surfaces of drum member 39 including the first arrangement 59 of copper tubing as well as the second arrangement 60 of copper tubing. However, the presence of spray nozzle head 75 at its location with exhaust stack 37 does provide sufficient cleansing action of the interior surfaces of exhust stack 37 as well as a majority of the first fan arrangement 22. This means that the exhaust stack 37 exiting from the kitchen portion of the restaurant will remain in virtually a grease-free status and will thereby preclude the presence of a fire hazard due to grease collection.

In order to deal with grease buildup which occurs on the internal surfaces of drum member 39 and the external surfaces of the first and second arrangements of copper tubing, branch line 76 extends upwardly and then inwardly to the approximate center of the hot exhaust gas flow stream which coincides with the approximate geometric center of drum member 39 and first fan arrangement 22. At this point, branch line 76 splits by means of a suitable fluid connection into spray nozzle heads 77 and 78 which are directed inwardly toward drum member 39 and outwardly toward the internal surfaces of cylindrical body member 54. These two spray nozzle heads are disposed on opposite sides of the cylindrical axis of drum member 39 in a generally symmetrical manner. The angular spray direction of each nozzle head as well as the angular separation between spray nozzle head 77 and spray nozzle head 78 may be varied, depending upon the particular size of drum member 39, the volume of exhaust gas, the amount of grease, and the rate at which drum member 39 is rotated. It is important to note that spray nozzle heads 77 and 78 are stationary with respect to main housing portion 21 and will create a fixed spray pattern with respect to the interior of drum member 39. As this chemical solution spray originating from source 70 is generated through nozzle heads 77 and 78, it will contact portions of the external surfaces of first arrangement 59 and second arrangement 60 as well as portions of the internal surface of cylindrical body member 54. This chemical solution spray places the grease which it contacts into an emulsified state. Some of this emulsified grease will be collected in the lower portion of body member 54 in a liquid carrier resulting from the excess spray liquid, and some will be placed into vapor form by the action of the hot exhaust gas which continues to flow through apparatus 20. This flowing hot exhaust gas is also effective to carry portions of the chemical solution spray to other regions of the drum member down stream from the location of spray nozzle heads 77 and 78. In this manner, virtually all areas of drum member 39 and arrangements 59 and 60 will receive a portion of the chemical solution spray mist. Inasmuch as spray nozzle heads 77 and 78 are stationary, it is not guaranteed that all areas of drum member 39 will be contacted due to inherent design inefficiencies in nozzle designs and positioning. For this reason, drum member 39 rotates at approximately one revolution per minute so that all regions can be guaranteed contact with the chemical solution spray mist. The grease removal from the external surfaces of first arrangement 59 and second arrangement 60 insure that high heat transfer efficiency will be maintained and that an insulating layer of grease will not be permitted to build up on these surfaces which would significantly reduce heat transfer.

Grease from within drum member 39 which is placed into a liquid mixture with the chemical solution will accumulate in the lowest level of drum member 39 and a drain outlet 79 is provided by which this liquid mixture may be removed from within drum member 39. Drain outlet 79 opens into a funnel member 80 which connects to drain tube 81 which ultimately flows to the drain system of the structure. It is possible for this grease and chemical solution mixture to congeal in the event the surrounding temperature is sufficiently low. Inasmuch as warm air is introduced beneath drum member 39 by means of second fan arrangement 23, the portion of drain tube 81 which is interior to apparatus 20 will remain warm enough so that the grease mixture will not congeal. However, when drain tube 81 exits from apparatus 20 on its way to the drain system of the structure, electrical tape 82 is wrapped around drain tube 81 thereby providing sufficient heat to retain the grease and chemical solution mixture in liquid form.

The emulsified grease which remains in vapor form as part of the hot exhaust gas will be circulated through drum member 39 and out end 48. Adjacent to end 48 of drum member 39 is a mist eliminator 61 (see FIGS. 4 and 5) which includes a plurality of evenly spaced tortuous passageways through which the exhaust gas must flow. These various passageways are separated by corrugated panels which have a plurality of rib-like hooks which alternately protrude from one side of each panel and then the other side. A suitable mist eliminator for this particular application is a model 921-22 offered by the Heil Process Equipment Company of Cleveland, Ohio. Panels 85 are thin-walled members measuring approximately 0.040 to 0.050 inches in thickness and the hooks 86 are spaced along the panels approximately every four inches. Such a mist eliminator is effective to remove approximately 99 percent of the liquid content of the gaseous flow which passes across and through the mist eliminator 61. This is the final stage which removes virtually all remaining grease from the exhaust gas circulating through apparatus 20. By taking the emulsified grease out of vapor form and converting it back into a liquid mixture, this being performed by mist eliminator 61, this remaining grease is able to be drained out of apparatus 20 by means of inclined drain pan 87 and drain tube 88 which couples to drain tube 81 by means of a suitable fluid connection. Now that virtually the entire grease content of the hot exhaust gas has been removed as well as a portion of the heat having already been extracted by means of first heat exchanger 58, subsequent heat removal can occur. This is accomplished by second heat exchanger 62 and then by third heat exchanger 63. Arrows 89 represent the flow path of the hot exhaust gas which exits from mist eliminator 61. This flow path is through second heat exchanger 62 which is constructed in much the same manner as an automobile radiator. Second heat exchanger 62 includes a plurality of closely-spaced fin members 90 through which this hot exhaust gas is permitted to flow. Running in a direction normal to this gas flow direction is a length of tubing which winds back and forth through second heat exchanger from one end to the other. A heat-absorptive fluid is provided to this length of tubing by means of fluid inlet 91. This heat-absorptive fluid is permitted to circulate through second heat exchanger 62 in that a return fluid outlet 92 is also provided at the opposite end of the length of tubing from fluid inlet 91. The exhaust gas flow which passes through and exits from second heat exchanger 62 will thereafter enter heat exchanger 63 and will have an exhaust gas flow therethrough as indicated by arrows 95. Third heat exchanger 63 is also arranged with a plurality of fin members 96 and a length of tubing extending through heat exchanger 63 in a direction normal to arrows 95 and is connected between fluid inlet 97 and fluid outlet 98. Inasmuch as the exhaust gas flow through second heat exchanger 62 has a maximum volumetric capacity, an alternate or escape route is also provided for exhaust gas flow which exceeds that maximum of heat exchanger 62. This alternative exhaust gas escape path 99 extends along the face of second heat exchanger 62 and around one end. From this point, this escape path extends between second heat exchanger 62 and third heat exchanger 63 to the opposite end of heat exchanger 63. At this point, the exhaust gas flowing through the escape path joins with that exhaust gas which has passed through third heat exchanger 63 and this combined flow is drawn down through connecting duct 32 into second fan arrangement 23. An intermediate duct section 100 is provided as an interface between connecting duct 32 and second fan arrangement 23. This intermediate duct section 100 is provided for structural and fabrication convenience in that it is rigidly secured to one flanged end of second fan arrangement 23 and joins with connecting duct 32 at its opposite side.

By the time the exhaust gas reaches second fan arrangement 23, all the heat which can be extracted has been extracted. Furthermore, the grease buildup within apparatus 20 as well as within exhaust stack 37, has been converted into a liquid mixture with the chemical solution and has been drained off to the drain system of the structure. The gaseous flow reaching second fan arrangement is still relatively warm and is now quite clean. This gaseous flow is directed across the lower portion of apparatus 20 for the providing of a heating blanket of air which has been previously mentioned.

This lower portion of apparatus 20 includes a structural shelf 103 which is supported on opposite sides by shelf brackets 104 and 105 which are bolted to adjacent frame leg members. Supported on structural shelf 103 are the various drive components for the drum member rotation and the circulation of the heat-absorptive fluid through the three heat exchangers. Drive motor 106 is an electric gear motor which is mechanically coupled by means of pulley 107 and drive belt 53 to drive rollers 46 and 47 which create a friction drive with drum member 39 as previously described. A suitable motor for drive motor 106 is a model 3M126A offered by Dayton Electric Manufacturing Company of Chicago, Illinois. Also located on structural shelf 103 at a position forward of drive motor 106 is an AC motor 108 which drives fluid pump 109. AC motor 108 is mechanically coupled to fluid pump 109 by means of a suitable arrangement of pulleys 110 and 111 and belt 112. A suitable motor for AC motor 108 is a model 5KC37NN3 offered by the General Electric Company. Also arranged as part of this lower portion of apparatus 20 are deflector plates 115 and 116 which are utilized to baffle and direct the flow of hot exhaust gas which exits from second fan arrangement 23 across structural shelf 103. These deflector plates permit a more uniform distribution of this hot exhaust gas so that all areas within apparatus 20 may be uniformly heated for a corresponding reduction of temperature gradient with the external atmosphere.

The first fan arrangement 22 and the second fan arrangement 23, although oppositely located, are driven in a similar manner. Although second fan arrangement 23 will be described in detail, the same is to be understood as applicable to first fan arrangement 22. The structural location and support of second fan arrangement 23 has previously been described. In that arrangement, a drive motor 117 is rigidly mounted to one of the frame leg members of the box-like frame structure for apparatus 20. This drive motor is mechanically coupled to second fan arrangement 23 by means of a suitable pulley 118 and continuous belt 119. In order to preserve proper belt tension between second fan arrangement and drive motor 117, drive motor 117 is rigidly secured to an intermediate plate member 120 which is arranged so as to slide inwardly or outwardly with respect to the structural frame leg member so that the length of belt 119 can be altered as is necessary. A similar arrangement is provided for drive motor 121 which is associated with first fan arrangement 22.

The use of first fan arrangement 22 in combination with second fan arrangement 23 provides a unique concept in that first fan arrangement 22 acts in a pushing manner, pushing the hot exhaust gas through the drum member 39. However, second fan arrangement 23 acts in a pulling manner, pulling the hot exhaust gas through drum member 39. The effect is that there is a zero pressure level created within the drum member in that there is neither an excess pressure nor a vacuum created and this contributes to the evenness and uniformity of the flow pattern through and across the various heat exchangers. This is desirable from the standpoint of maximum efficiency and uniform heat transfer. A suitable device for both first fan arrangement 22 and second fan arrangement 23 is a Dayton model 7C411 offered by W. W. Grainger, Inc. Inasmuch as a model 7C411 fan is operable at either 1,150 RPM or 1,725 RPM with a free air flow rate of 4,000 CFM, it is possible to create any one of eight different combinations of fan utilization by means of either turning one fan arrangement off or on and if on at one of its two speed settings. A further feature associated with first fan arrangement 22 involves the relative diameter sizes of exhaust stack 37 with respect to cylindrical body member 54 of drum member 39. Exhaust stack 37 measures approximately 12 to 14 inches in diameter while cylindrical body member measures approximately 18 inches in diameter. Consequently, when the hot exhaust gas flowing through exhaust stack 37 enters cylindrical body member 54, its flow velocity will be significantly reduced in proportion to the cross-sectional area of these diameter measurements. This reduced exhaust gas speed flow means that heat transfer to the first and second arrangements of copper tubing of the first heat exchanger will be enhanced. If the exhaust gas flow speed was too fast, a greater portion of the heat would pass through to second fan arrangement 23 and would not be able to be utilized for the heat transfer by means of the various heat exchangers.

Referring to FIG. 7, the flow pattern of the heat-absorptive fluid is illustrated. Returning heat-absorptive fluid which is at a relatively low temperature is introduced into apparatus 20 at point 125. Cut-off valves 126 and 127 are provided on either side of fluid pump 109. A suitable fluid pump for this application is a model 1P830 offered by Teel Manufacturing Company of Chicago, Illinois. This fluid pump operates at approximately 1,200 RPM and provides approximately 10 gallons per minute. Dial indicator 24 indicates the temperature of this incoming heat-absorptive fluid and after indicator 24, the flow path splits into three separate branches. The first branch 128 supplies heat-absorptive fluid to first heat exchanger 58 which is located within drum member 39. Rotary joints 129 and 130 are provided so that the first heat exchanger is able to rotate with drum member 39 while the connecting fluid tubing remains stationary. Second branch 131 couples to second heat exchanger 62 while third branch 132 couples to third heat exchanger 63. The return lines 128a, 131a and 132a connect at common point fitting 135 where they reunite into a single flow path. Dial indicator 25 indicates the temperature of this heat-absorptive fluid after heat transfer from the hot exhaust gas to this heat-absorptive fluid has occurred simultaneously within the three different heat exchangers. This single flow path indicated by pipe 136 extends to a remote location where it couples to additional heat exchangers. Such heat exchangers may be a finned arrangement located in combination with the cold air return duct of the conventional heating system for the particular structure. In this manner, the hot heat-absorptive fluid in flow pipe 136 will be transferred to these remote heat exchangers at which point heat transfer from the heat-absorptive fluid to the passing cold air will take place and will provide heat to the interior of the structure as a supplement to the conventional heating system. A point of split 137 is illustrated in FIG. 7 as representative of the flow split from flow pipe 136 when a plurality of remotely located heat exchangers are involved. The remaining dial indicators 26, 27 and 28 indicate the temperature of the entering hot exhaust gas, the temperature of the exhaust gas as it leaves second fan arrangement 23 and the fluid pressure being pumped through the various heat exchangers.

Referring to FIG. 8, a block diagram is provided of the exhaust gas flow through apparatus 20. The first stage is through the first fan arrangement 22. From that point, the hot exhaust gas is passed through and across first heat exchanger 58 which has fluid flow lines communicating therewith. After first heat exchanger 58, the hot exhaust gas which now has had a portion of the grease removed therefrom as well as a portion of its heat, flows through mist eliminator 61 which extracts the remaining vapor within this gaseous flow. After mist eliminator, the exhaust gas flows through and across second heat exchanger 62 which also includes fluid connections communicating therewith and from there to third heat exchanger 63 also including fluid connections communicating therewith. The final stage of flow for the exhaust gas is through the second fan arrangement and then into the lower portion of apparatus 20.

A further feature of apparatus 20 is illustrated by FIG. 6 which shows in fragmentary form the mounting of first fan arrangement 22 onto the first end 40 of apparatus 20. As previously described, apparatus 20 includes a structural frame portion which includes a series of aluminum angles and square aluminum tubing rigidly secured together. These structural frame members are indicated as upright frame members 138 and cross members 139. Inasmuch as these frame members provide a box-like frame structure into which drum member 39 is located, there remain corner areas disposed at the first end of member 39 which create an inefficient arrangement. Consequently, a skin sheet 140 having a circular opening therein which is slightly larger than the diameter of cylindrical body member 54 is rigidly attached over first end 40. Bonded to the outer surface of this skin sheet 140 are a plurality of strips 141 of rubber material. These strips 141 are arranged in a generally frame-like orientation substantially coincident with frame members 138 and 139. On top of these rubber strips 141 the flange 142 at flanged end 41 of first fan arrangment 22 is rigidly attached through strips 141 into frame members 138 and 139 and is secured thereto by means of three bolts 143. The fourth point of attachment of flange 142 to frame member 138 and 139 is by means of pivot pin 144. Once the fan arrangement 22 is discconnected from exhaust stack 37 and the three bolts 143 are each removed, first fan arrangement 22 is permitted to pivotally swing downwardly and out of the way of drum member 39 by means of pivot pin 144. This is desirable in the event spray nozzle heads 77 and 78 would need to be adjusted, repaired or replaced. Similarly, the first fan arrangement can be pivotally swung out of the way in the event minor repair, cleaning or other overhaul related work is desired to be performed on apparatus 20.

It can be seen then that what has been described by the foregoing description is a modular unit which can conveniently tie into an existing exhaust stack of a structure such as a restaurant. The various utility connections of apparatus 20 can be accomplished in a somewhat typical manner. Power box 147 is provided on the side of apparatus 20 for coupling the requisite electrical power to the various motors associated with apparatus 20. Similarly, drain tube 81 can be routed to the drain system of the structure and the entire unit can be rigidly secured to a rooftop level. By providing source 70 of chemical solution as part of apparatus 20, a minimum of fluid connections external to apparatus 20 are required. It should be noted, however, that source 70 of chemical solution may also include as part of it a supply of water 150 such that once the chemical solution is sprayed onto the internal surfaces of apparatus 20 and begins the emuslifying of the grease, that a water rinse may be desirable to flush away this emulsified grease in liquid form. Although various chemical solutions can be used, the selection of which solution depends upon the nature of the contaminant which is within the exhaust stream. A major contaminant material is believed to be grease as has been described, however, other contaminant substances can be removed from their corresponding gaseous flow stream by the selection of a proper chemical solution in which the particular contaminant material is soluble. A further feature is that the chemical solution need not be sprayed in a continuous manner but rather is sprayed in a pulsating manner. This permits the chemical solution to be sprayed onto a particular area of apparatus 20 and then remain there while its chemical action operates on the grease buildup. Then, a time interval later, a rinse of water is also pulsated across this same area thereby rinsing away the emulsified grease. In the preferred embodiment, water is pulsated in an on and off spray manner for approximately 50 minutes out of each hour. This pulsating spray mist of water is on for approximately 30 seconds and is then off for a corresponding 30 seconds. At the end of a 50-minute time interval, a chemical solution, such as a detergent, is pulse-sprayed in 30-second on and 30-second off intervals for approximately 10 minutes. This procedure conserves the chemical solution yet provides a sufficient amount for the emulsifying of the grease without excess and waste. Similarly, the mist sprayed is so fine that only approximately four gallons of water are used per hour. By having a continuously pulsating spray of water or chemical solution, the entire system is maintained in a wet condition. This means that fire starting is quite unlikely for two reasons. The first reason is that grease buildup is virtually eliminated from within apparatus 20 and the second reason is that the internal portions of apparatus 20 remain in a wet condition.

Although hot exhaust gas has been referred to, it is to be understood that the air-cleaning, heat-exchange apparatus disclosed herein also finds applicability as a cooling apparatus. In lieu of hot exhaust gas, consider any gaseous flow from a structure, such as ambient air, which has a temperature higher than the temperature of the heat-absorptive fluid circulating through the various heat-exchange means. A cooling coil in communication with the heat-absorptive fluid will provide a sufficient temperature difference for this application. Heat transfer will occur thereby resulting in a gaseous flow output from apparatus 20 which has a lower temperature than the entering flow. This output flow could then be introduced back into the structure for cooling. During this cooling mode of operation, the gaseous flow may still be chemically treated as has been described in order to remove any contaminants and especially odors from the ambient air.

A further feature of apparatus 20 is that the heat transfer (heat recovery) aspect of operation and the contaminant-removal aspect of operation are separate and distinct operational modes. The heat recovery mode may be used selectively as an option, while the contaminant removal (cleaning mode) goes on continuously with the operation of apparatus 20.

While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiment has been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.